Field of the Invention
This invention relates generally to retreaded tires, and more particularly, to retreaded tires with improved evacuation of gas from between the tread and tire carcass.
Description of the Related Art
It is commonly known to form a retreaded tire by attaching a precured tread to a tire carcass. The tread is typically pre-formed into a strip having a tread pattern, and is then applied around the circumference of a prepared tire carcass. The tire carcass is typically prepared by removing the old tread and a layer of cushion gum or liaison rubber is applied to the tire carcass prior to receiving the new tread.
In prior methods, after the retreaded tire is assembled, the retreaded tire is placed at least partially within a flexible curing membrane, or envelope, to create a fluid chamber between the curing membrane and the tire. The retread tire assembly with the envelope is placed within a curing chamber, often referred to as an autoclave, where the membrane-covered assembly is exposed to heat and pressure according to a desired curing process to bond the tread to the tire carcass. Before and during the early portion of the curing cycle, substantially all of the air or other gases between the tire and envelope is removed by a vacuum source. Evacuating gas from between the tire and the envelope forces the flexible membrane against the tread and tire carcass. As the curing cycle progresses, the compartment between the tire and envelope is maintained at the same or a lower pressure than the pressure in the curing vessel outside of the envelope. The prior processes using curing membranes have drawbacks, such as inefficiency in handling and installing the membranes over the tire assembly, a limited number of curing cycles the membranes withstand before they have to be replaced, and for certain tread designs, the pressure differential used in prior processes could cause deformation or bulging at the bottom of grooves in the tread.
Certain prior methods have attempted different ways to evacuate gas from between the tread and tire carcass. It would be advantageous to improve evacuation of gas from between the tread and tire carcass.